Fixing an Over-reading Tach

Date: Sun, 5 Jul 1998 11:14:51 -0400 (EDT)
From: Paul Burr
Subject: Re: Tach befuddling behavior resolved but explanation required

At 3:19 PM -0000 7/4/98, jaltman@altlaw.com wrote:
>I cleaned the cable and put it back in. Started the engine and noticed I had
>not tightened the cable down, it was reading correct. I tightened it up, it
>rose back to 50% high. I cut about 5/8" off it and put back in. If I
>tighten it all the way down it still reads high, but if I leave the nut
>about 2/3 loose it reads fine.
>
>Sounds like the cable is a bit too long, but why would that make any
>difference?

I had the speedo wrecked by a replacement cable in my Tiger. When I had it rebuilt by MOMA (see monster list, nice people to deal with!) they explained that replacement tach cables often have too much cable protruding into the gauge. This causes premature internal wear and all kinds of readings weirdness. This might be what you're up against.

Paul Burr

Moral: Doublecheck your replacement part tolerances, especially if a more expensive part depends on them as is often the case. -JB